Turbine guide vane

ABSTRACT

A turbine guide vane ( 10 ) has a platform ( 12 ) from which at least a guide vane blade ( 13 ) extends. The platform ( 12 ) has a front rail ( 18 ) and a rear rail ( 20 ) arranged to be housed in guide vane carrier seats ( 19, 21 ). The front and rear rails ( 18, 20 ) have projecting pads ( 23, 24 ) arranged to rest against the guide vane carrier seats ( 19, 21 ). The front and rear rails ( 18, 20 ) have at least two pads ( 23 ) extending from one side of the front and rear rails ( 18, 20 ) and at least two further pads ( 24 ) extending from an opposite side of the front and rear rails ( 18, 20 ). The pads ( 23, 24 ) extend from opposite circumferential portions ( 26 ) of the front and rear rails ( 18, 20 ). The pads ( 23, 24 ) extending from the same circumferential portion ( 26 ) of the front and rear rails ( 18, 20 ) are at least partly staggered with respect to one another.

This application claims priority under 35 U.S.C. §119 to European application no. No. 10152535.0, filed 3 Feb. 2010, the entirety of which is incorporated by reference herein.

BACKGROUND

1. Field of Endeavor

The present invention relates to a turbine guide vane.

In particular the present invention refers to a supporting system for turbine guide vanes.

2. Brief Description of the Related Art

Gas turbine guide vanes are known to have a platform from which one or more guide vane blades extend.

For example, in guide vanes of the third or fourth stage, from each platform two or three guide vane blades extend.

The platforms have a front rail and a rear rail arranged to be inserted into guide vane carrier seats having a slot shape.

When in operation, mechanical forces and thermally induced deformations highly stress the guide vane rails and the guide vane carriers.

For this reason, the shape of the rails must allow free deformations in order to avoid stress concentration and breakage risk.

FIG. 1 shows a first embodiment of a traditional rail 1 inserted into a guide vane carrier seat 2 (in this figure the dimensions are exaggerated for sake of clarity, particularly radial dimensions are exaggerated); moreover, FIG. 1 also shows in dashed line a portion of a guide vane blade 3.

The rail 1 has a pad 4, extending from its side towards the guide vane blades 3, resting against the guide vane carrier seat 2; a second pad 5 extends from the side of the rail 1 opposite the guide vane blade 3 and rests against the guide vane carrier seat 2.

The guide vane in this traditional embodiment proved to have good deformation properties and also ease of assembly (i.e., sliding of the rail 1 into the guide vane carrier seat 2 proved to be easy); nevertheless, this structure can only be implemented in lighter guide vanes, i.e., typically in guide vanes having only one or two guide vane blades 3.

FIG. 2 shows a different embodiment of traditional rails.

This rail 1 is provided with pads 6 extending from the same side, that being the side of the rail 1 towards the guide vane blade 3; the opposite side of the rail 1 has no pads and rests directly against the guide vane carrier seat 2.

The guide vanes with these rails can be much heavier than those with the rails of FIG. 1, for example these guide vanes can have three or more guide vane blades.

Nevertheless these guide vanes have limited freedom of deformation; this could cause, during operation, stress and force concentration and consequently the possibility of structural breakages.

In addition, assembling (sliding the rails of these guide vanes into the corresponding guide vane carrier seats 2) and disassembling (sliding the rails out of the guide vane carrier seats 2) proved to be very difficult, because of the weight of these guide vanes and the large surfaces of the rails and guide vane carrier seats that are directly in contact with one another.

U.S. Pat. No. 7,458,772 discloses guides vanes with four pads (two upper and two lower pads); the pads are not staggered.

DE 1 476 928 discloses a blade with a platform and pads, which are not staggered.

U.S. Pat. No. 5,205,708 discloses a rail of a high pressure turbine blade having two pads at one side and one single pad at the opposite side; when inserted into the housing the rail generates a spring effect.

SUMMARY

One of numerous aspects of the present invention includes a guide vane by which the aforementioned problems of the known art are addressed.

Another aspect of the present invention includes a guide vane that can have a substantial weight and, in this respect, can also have three or more guide vane blades.

Another aspect includes a guide vane with rails having large deformation possibilities, such that during operation stress and force concentrations are avoided or limited and the lifetime of the guide vanes is increased.

A further aspect includes a guide vane that can be easily and quickly assembled and disassembled.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will be more apparent from the description of a preferred but non-exclusive embodiment of the guide vane according to principles of the invention, illustrated by way of non-limiting example in the accompanying drawings, in which:

FIGS. 1 and 2 are two different embodiments of rails of a guide vane of the prior art;

FIG. 3 is a side view of a guide vane in an embodiment of the invention; and

FIGS. 4 and 5 are views respectively of a front rail and rear rail of the guide vanes; in these figures the dimensions (in particular radial dimensions) are exaggerated for clarity.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

With reference to FIGS. 3-5, a turbine guide vane 10 is illustrated.

The guide vane 10 has a platform 12 from which guide vane blades 13 extend; in particular FIG. 3 shows an embodiment of a guide vane 10 with three guide vane blades 13, it is anyhow clear that in different embodiments their number can also be different.

The guide vane 10 is also provided with a support located at the front side and rear side of the platform 12 (with reference to the hot gas flow direction indicated by arrow F in FIG. 3).

In particular, the front side of the platform 12 has a seat 15 for the stator heat shield and, correspondingly, the rear side of the platform 12 has a seat 16 for a further stator heat shield (the stator heat shields are not shown).

In addition, the front side of the platform 12 has a rail 18 arranged to be housed in a guide vane carrier seat 19; the guide vane carrier seat 19 is of traditional type and has the shape of a circumferential slot.

Similarly, the rear side of the platform 12 has a rail 20 arranged to be housed in a guide vane carrier seat 21; also the guide vane carrier seat 21 is of traditional type and has the shape of a circumferential slot.

The rails 18 and 20 have projecting pads arranged to rest against the guide vane carrier seats 19, 21.

Advantageously, each rail 18, 20 has two pads 23 extending from one side of the rail and two further pads 24 extending from an opposite side of the rail 18, 20.

In particular, as shown in the figures, the pads 23 and 24 extend from opposite radial sides of each rail 18, 20; the pads 23 extend from a side of the rails 18, 20 facing the guide vane blades 13, and the other pads 24 extend from the opposite side, i.e., from the side opposite the guide vane blades 13.

In addition, the pads 23 and 24 extend from opposite circumferential portions 26 of the rails 18, 20, i.e., they are located close to the circumferentially opposite ends of the rails 18, 20.

The pads 23, 24 that extend from the same circumferential portion 26 of the rails 18, 20 are advantageously at least partly staggered with respect to one another.

In this respect FIG. 4 (referring to the front rail 18) shows the pads 23 and 24 that are staggered but are circumferentially very close one to the other.

FIG. 5 (referring to the rear rail 20) shows that the pads 23 and 24 that are staggered are also circumferentially distant one from the other.

In addition, in each pair of pads 23, 24 extending from the same circumferential portion 26 of each rail 18, 20, the pads 23 extending from the side of the rail facing the guide vane blades 13 are farther from the respective rail end 27 than those opposite the guide vanes blades 13 (i.e., the pads 24).

In a particular embodiment the pads 23 and 24 are symmetrically disposed with respect to the vane axis 28; it is anyhow clear that in different embodiments the pads 23 and 24 are not symmetrically disposed with respect to the vane axis 28.

Assembling of the guide vanes embodying principles of the present invention is quite easy and fast, because the rails 18 and 20 are inserted into the guide vane carriers seats 19, 21 and are made to slide into the seats.

Since the contact occurs only between the pads 23, 24 and the guide vane carrier seat 19, 21, and since, when the rails 18, 20 are housed in the guide vane carrier seats 19, 21 preferably a certain gap between the pads 24 and the same guide vane carrier seats 19, 21 is provided, rails slide with limited friction. In addition, pads staggering makes rail introduction into the seats 19, 21 very easy.

Also, disassembling is easy and quick; in fact, since there are no large contact surfaces between the rails 18, 20 and the guide vane carrier seats 19, 21, there is little or no risk that dust or deformations due to mechanical forces and thermal stress block the rails 18, 20 inside of the guide vane carrier seats 19, 21.

In addition, the guide vanes of the invention may also have a heavy structure (such as for example guide vanes having three or more guide vane blades 13), since assembling/disassembling is easy and the degree of allowable deformations is very large.

In fact, when the guide vanes 18, 20 are assembled within the guide vane carrier seats 19, 21, deformations can freely occur in a large extent, because space and support are always available.

Naturally the features described may be independently provided from one another.

In practice the materials used and the dimensions are chosen according to requirements and to the state of the art.

Reference Numbers

1 rail

2 guide vane carrier seat

3 guide vane blade

4 pad

5 pad

6 pad

10 guide vane

12 platform

13 guide vane blades

15, 16 seat for the stator heat shield

18 front rail

19 guide vane carrier seat of 18

20 rear rail

21 guide vane carrier seat of 20

23 pad

24 pad

26 portion of 18, 20

27 rail end

28 guide vane axis

F flow gas direction

While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein. 

1. A guide vane of a gas turbine, the gas turbine including guide vane carrier seats, the guide vane comprising: a platform; and at least one guide vane blade extending from the platform; wherein said platform has a front rail and a rear rail configured and arranged to be housed in the guide vane carrier seats, said front and rear rails having projecting pads configured and arranged to rest against the guide vane carrier seats, said front and rear rails having at least two first pads extending from one side of the front and rear rails and at least two second pads extending from an opposite side of the front and rear rails, said pads extending from opposite circumferential portions of the front and rear rails, and said pads extending from the same circumferential portion of the front and rear rails being at least partly staggered with respect to one another.
 2. A guide vane as claimed in claim 1, wherein said pads extend from opposite radial sides of said front and rear rails.
 3. A guide vane as claimed in claim 2, wherein said pads extend from a side of the front and rear rails facing the guide vane blade, and from a side opposite the guide vane blades.
 4. A guide vane as claimed in claim 1, wherein: one of each of the first and second pads form a pair; each pair of pads is located at the same circumferential portion of each front and rear rail; and the pads extending from the side of the front and rear rails facing the guide vane blades are farther from the respective rail end than those opposite the guide vanes blades.
 5. A guide vane as claimed in claim 1, wherein: the guide vane defines an axis; and said pads are symmetrically disposed with respect to the guide vane axis.
 6. A guide vane as claimed in claim 1, wherein: the guide vane defines an axis; and said pads are not symmetrically disposed with respect to the guide vane axis.
 7. A guide vane as claimed in claim 1, wherein said at least one guide vane blade comprises a plurality of guide vane blades.
 8. A guide vane as claimed in claim 7, wherein said plurality of guide vane blades comprises at least three guide vane blades.
 9. A guide vane as claimed in claim 1, wherein the rails and the pads are configured and arranged so that, when the rails are housed in the guide vane carrier seats, a gap is formed between the pads and the guide vane carrier seats. 